The present invention relates to a gas heating appliance and in particular to an electronically controlled gas heater.
The invention has been developed primarily for use in domestic gas space heaters and will be described hereinafter with reference to this application. However, it will be appreciated that the invention is not limited to this particular field of use.
Gas heaters are popular due to their low costs, both capital and on-going, and their high heating capacity. However, increasing awareness of the dangers of emissions of oxides of nitrogen (NOx), particularly in flueless heaters, has seen a corresponding increase in the amount of regulation surrounding such heaters.
One way to reduce NOx emission from a gas heater has been to optimize the combustion chamber and burner designs, and air injection systems. However, in the past such optimization has generally occurred in the physical size and layout of the chamber, and crude pre-setting of a minimum of a heater's many possible operating parameters.
Another major concern, with flueless gas heaters in particular, is the depletion of oxygen which takes place in a poorly ventilated room. As oxygen (O.sub.2) is consumed, carbon dioxide (CO.sub.2) builds up and can provide a health risk for the persons in the room.
Flashback is a condition where the flame is inside of the burner rather than on top of the combustion surface. To prevent destruction of the burner under flashback conditions, the typical heater has required a burner that is substantially more rugged, heavy and expensive than otherwise needed.
Also, the ability to change the operating parameters of such a device during manufacture and after installation has been severely limited in scope. Reliance has been placed upon test equipment external to the device or rudimentary electronic controls.